Free Embryonic Development MCQs with Answers

21. In which stage of development, germ layers are formed?

• A. Morulation
• B. Blastulation
• C. Gastrulation
• D. Organogenesis

Explanation: Germ layers that are ectoderm, endoderm, and mesoderm are formed during gastrulation. During gastrulation, the blastoderm splits into two layers: an upper layer of cells called epiblast and a lower layer of cells called hypoblast. The epiblast is the presumptive ectoderm and mesoderm while the hypoblast is the presumptive endoderm.

22. Microcephaly, the small sized skull is due to:

• A. Nutritional Cause
• B. Hormonal Causes
• C. Skeleton Damage
• D. Genetic Defect

Explanation: Explanation: Microcephaly, the small-sized skull, is usually due to a genetic defect. It can also be caused by environmental factors such as infections, exposure to toxic substances, and lack of proper nutrition during fetal development, but genetic causes are the most common. Genetic causes may include mutations in genes involved in brain development, chromosomal abnormalities, or inherited conditions that affect brain growth.

23. At the cephalic end of primitive streak, closely packed cells form a loci thickening known as:

• A. Hensen's Node
• B. Primitive Ridge
• C. Gastrocoel
• D. Primitive Gut

Explanation: Explanation:At the cephalic end of the primitive streak, closely packed cells form a locai thickening known as Hensen's node. It is the site where the gastrulation begins and the 3 germ layers are first formed.This option is not correct. The primitive ridge is a thickened area of the ectoderm that lies above the notochord in the developing embryo. It is formed during neurulation and serves as a signaling center that regulates the patterning of the neural tube.This option is also incorrect. The gastrocoel is a cavity that forms in the developing embryo as the gut tube forms by folding the endodermal layer. It eventually becomes the lumen of the developing digestive tract.This option is also incorrect. The primitive gut is the initial tube-like structure that develops from the endoderm during gastrulation. It later gives rise to the digestive tract and associated organs.

24. Grey equatorial cytoplasm produces:

• A. Muscle cells
• B. Gut
• C. Notochord and neural tube
• D. Larval epidermis

Explanation: [A]Sarcoplasm is the cytoplasm of muscle cell which is yellow in colour[B] Gut is produced by grey vegetal cytoplasm[C] Notochord and neural tubules are produced by Grey editorial cytoplasm[D] Larval epidermis is produced by clear cytoplasm

25. The nervous system develops from which of the following layer during embryonic development of animals?

• A. Mesoderm
• B. Ectoderm
• C. Endoderm
• D. Mesoderm and Endoderm

Explanation: Option [A]Mesoderm gives rise to muscular,skeletal and reproductive systemsOption [B] After embryonic development the body layers[ ectoderm, mesoderm and endoderm] in most triploblastic animals are represented by the structures formed from them. The systems such as integumentary and nervous system develop from Option [C] Endoderm forms the lining of the digestive tract and forms other glands of the digestive system, such as the liver.Option [D] Mesoderm and Endoderm [same as above]